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E39 (1997 - 2003) The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

Four days ago I noticed that the rubber intake fitting that goes over the throttle body was ripped. To fix the issue I went down to my local performance shop to see if I can find a rubber/silicone coupling to fix the problem. While there I got to talking about a CAI and discovered that the shop had something I was looking for 3 years (I know it sounds too dramatic). It was a very high quality flex pipe. It was made with 3 layers of silicone and layers of nylon rope and metal coil. Really high quality stuff. Seeing this made me want to expand my project from fixing the ripped fitting to installing a full CAI, a real CAI, the kind I always envisioned, not the kind that mounts the filter under the hood. So with parts in hand I set off to undertake what I thought would be a relatively straight forward project.

The first surprise came when after taking off stock air box, the bumper and headlights. I think the word Iím looking for is shocked to describe the size, shape and general setup of the stock intake plumbing. Not only was the intake hole tiny, it faced towards the rear of the car and sucked in air right in front of the auxiliary fan. (So if the fan is on, it basically sucks air out of the intake.) I guess it was all made that way to make the 4.4L V8 quiet enough for soccer moms, but for me it was horrible. See pictures below.

Then using the flex pipe and an Autozone cone filter I went to work. For a rather large sedan, itís surprising how very very little room there is under the hood for any kind of modifications. There is literally just 1 or 2 millimeters of extra space for components (sometimes zero). I had to fight through the project the entire way. Starting from making sure the fan blades donít hit the MAF/Intake piping, to going crazy trying to fit the flex pipe between the stupid secondary air pump, the bumper and my fog lights, to finally finding a suitable place for the filter. It took me a total of 8 hours to put anything together, but man am I glad I did it. The car sounds absolutely amazing. I will try to post a sound bite later.
Anyways, enough talk, here are all the pics.

How do you know how this is better than Dinan? Just on the sound alone? From other people installing CAI's on their cars, they have shown to have almost 0 performance gains. The only thing that comes from it is the sound.. I guess if the sound was what you're looking for than more power to you, but i would have fixed that torn up bumper and removed those eyelids before i did any other modifications

EDIT: BMW has done these sort of things for the air getting to the engine for a reason, no matter how long or messed up you find it to be..it still works the way it should. hence why putting a cai on it does almost nothing except make some noise and break your wallet when you could put that towards a new bumper.

I got to give you that one. I forgot the kind of people that are on the BMW forums, but I'm very quickly being reminded of it. Good thing the owner manual did not say "Jump of a bridge", if it did, most of you people would not be here.

I only have a basic understanding of why CAI is mostly worthless, but the gist is that more air is not necessarily a good thing. For any given throttle position except wide open throttle, the engine only needs a certain amount of air, and the stock system is more than adequate to provide that. At wide open throttle, a CAI probably lets the engine suck in more air, but at what cost? And how much are you actually gaining, other than noise? A couple HP at most?

Quote:

Originally Posted by 540ig5

That's just silly

No, what's silly is what you did to that car. You don't think you massively increased the risk of sucking up water with the filter being that low? What happens if you hit a puddle, or drive behind someone who is kicking up heavy mist? What about in the winter, not worried about snow? Eventually the filter will get saturated enough that it starts pulling in water, or during winter it could become encrusted with ice and choke the engine.

I'm all for DIY that improves a car in one way or another, but there is nothing good about what you've done here. I just hope there's enough backlash in this thread to prevent any hapless googler from trying it themselves.

Man looking closer at your pics this car needs a lot of work. I mean wow. I'd stop spending $80 to piece together a ghetto CAI and start saving up for stuff like an engine cover, paint for your headlight trim, goo be gone after yanking off those cheesy eyelids, replacement brake duct intake tubing, bumper paint, I could go on but you get the gist. Goodluck my friend.

OP do you plan on removing it when it rains, if not, you're looking for a whole mess of trouble. It is unprotected from the elements sitting in that position. That is the reason why most aftermarket manufactures of CAI design them for under the hood to save them from liability of naive enthusiast.

OP do you plan on removing it when it rains, if not, you're looking for a whole mess of trouble. It is unprotected from the elements sitting in that position. That is the reason why most aftermarket manufactures of CAI design them for under the hood to save them from liability of naive enthusiast.

shhh

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OP do you plan on removing it when it rains, if not, you're looking for a whole mess of trouble. It is unprotected from the elements sitting in that position. That is the reason why most aftermarket manufactures of CAI design them for under the hood to save them from liability of naive enthusiast.